something.js

// first part
(function()
{
  window.ext = {};
  var MyClass = ext.MyClass = function() {
    this.foo = 'bar';
  };
  MyClass.prototype = {
    func1: function() {
        ...
    },
    func2: function() {
        ...
    }
  };
})();

// Second part
(function() {
  ext.anObject = new ext.MyClass();
})();